The present invention relates to ring generator wheels for use in grinding of toric lenses in the ophthalmic industry. More particularly, the present invention relates to fly cutter type ring generator wheels which include the combination of a polycrystalline diamond blade with an abrasive grit material thereon on the cutting edge of the wheel.
In recent years there have been several advances in ring generator wheels useful in grinding toric curves in ophthalmic lenses. One highly advantageous improvement has been the use of single or multiple polycrystalline diamond fly cutter blades in combination with an abrasive grit material provided on the radius, inner and outer circumference of the rim portion of the generator wheel. Such generator wheel constructions have increased the efficiency when forming these lenses and have been a great improvement in the ring generator wheel art.
These combination wheels have been found extremely advantageous in concave or "minus" type lenses, however some problems have been experienced when such a wheel is used with "plus" type lenses. During forming of "plus" type lenses with such a wheel, the lenses have tended to chip at the edges unless special procedures or precautions are taken. It was at first thought that the chipping of these "plus" type lenses was caused by the use of the fly cutter blade since chipping was not generally experienced when a standard ring generator wheel having abrasive grit attached was used. However, when utilizing a fly cutter wheel with only blades and no grit attached the problem also did not occur. Thus, the problem was unique to the new combination wheel which includes fly cutter blades and abrasive grit attached thereto. In order to attempt to alleviate this problem it was often necessary when using these new wheels to "back cut" into the lens prior to making the main cut in the lens. Such a technique tended to reduce but did not eliminate chipping at the edges thereof. While such a process is inconvenient for the final user, this process could still accomplish a finished "cut" faster than conventional wheels and therefore was very useful. With recent improvements in such fly cutter wheels and the like, such as that shown in co-pending application Ser. No. 579,869, filed Sept. 6, 1990 by Ronald C. Wiand and entitled: "Cutting Tool With Polycrystalline Diamond Segment and Abrasive", such structures are increasingly becoming more advantageous and effective in the lens cutting and ophthalmic industry.
It has thus been a goal in the art to provide an improved fly cutter wheel which would eliminate this chipping problem thereby reducing the back cutting step and eliminating propensities for edge chipping of lenses. It is therefore, an object of the present invention to provide an improved fly cutter type generator wheel which will eliminate the step of back cutting of lenses and will reduce propensities for lens chipping in the ophthalmic lens forming industry.